[Colonic motility]

Colonic motility is provided by contraction of intramural smooth muscle under the control of the enteric and the extrinsic nervous system and humoral connections. In vivo measurement of colonic motility remains difficult because of the complexity of these interactions and anatomical considerations. The possibility that symptoms are due to colonic dysmotility should be considered in patients with normal barium enema and colonoscopy. Examples of this are patients with chronic constipation, irritable bowel syndrome or colonic symptoms associated with diabetes mellitus or diseases of the nervous system. A number of techniques have been developed to assess colonic motility. The simplest is to assess colonic transient with a single abdominal x-ray following ingestion of radio-opaque markers. This is cheap, reproducible and easy to perform. Normal values for age and sex are available. Colonic transit of both liquid and solid can be determined by scintigraphic measurement. This technique provides information about regional variations in colonic function; it is however relatively demanding and requires access to a gamma camera. Manometry provides a more direct assessment of colonic motor activity. Changes in the electrical potential of the colonic smooth muscle can be determined by electromyography. Both techniques are however difficult to perform, and are currently only used for research purposes. It is likely that the combination of techniques that examine transit with more direct measurement of motor function will provide further insights into the mechanisms responsible for colonic dysmotility.